Following the launch of macOS 12.3, the addition of Universal Control has been overshadowed by reports that many Mac users are finding that external monitors no longer work.
UPDATE: On March 31, 2022, Apple issued an update to Monterey. macOS 12.3.1 fixes screen fixes – specifically fixes a screen issue with Mac mini, which may mean that this issue with screens introduced in macOS 12.3 has now been fixed. However, Apple’s release notes refer to a problem with USB-C or Thunderbolt monitors that do not turn on when connected to a 2018 Mac mini as a second monitor. In our case, the problem relates to an M1 Mac mini (see details below).
The day after I installed macOS 12.3, one of the two monitors I use (an LG) with my Mac mini started working intermittently. At intervals, it would just turn off and then on again. I would wiggle the cables, turn them on and off again, but nothing seemed to solve the problem.
Eventually I switched it to a spare screen (a Dell) and thought no more about it … until I found out that others were experiencing the same thing.
There were reports (via Apple Discussions) from some users that a previously functioning screen could no longer be detected. In my case, I used an HDMI connection, but other reports suggested that it was related to USB-C and Thunderbolt. Mine is an M1 Mac, but it sounds like the issue is also affecting Intel Macs.
How to fix display issues in macOS 12.3
The problem may be related to the DisplayPort 1.4 protocol. One user reported that after changing the protocol version from 1.4 to the older version 1.2, he was able to use his monitor again. But there were also reports that switching from 1.2 to 1.4 also solved the problem.
Other users could check their monitor again after disconnecting, unplugging it from the mains and reconnecting it, others by switching to HDMI.
There is no feedback from Apple on the subject yet.
This article was originally published on Macwelt. Translation by Karen Haslam.